A sewing system has been conventionally developed in which a sewing machine is mounted on a tip portion of a robot arm and stitching is performed not only on a flat surface but also on a curved surface having a three-dimensional shape.
In such a sewing system, when a three-dimensionally shaped workpiece is set between the throat plate and the lower end portion of the sewing needle at the start of sewing, it was necessary to open the space between the throat plate and the lower end portion of the sewing needle to be wider than the case of a planar workpiece.
However, even if the sewing needle is lifted to the top dead center position to the maximum extent, the distance between the throat plate and the lower end portion of the needle is insufficient, and a structure for enlarging the distance therebetween is separately required.
Thus, it has been studied to apply a sewing machine having a mechanism for allowing the end portion on the surface portion side of an arm portion to move up and down together with the needle bar with respect to the needle plate to the robot arm (for example, see Japanese Patent Application Laid-open Publication No. 05-305193).
However, in the above-mentioned sewing machine, since the surface side end portion of the arm portion performs lifting and lowering a frame, when the sewing machine is to be mounted on the robot arm, the position of the robot arm for holding the frame needs to be located at a position spaced apart from the surface side end portion to avoid the movable portion of the arm portion. Thus the distance from the tip portion of the robot arm to the stitch point position of the sewing machine was too long, and it was difficult to increase the positioning accuracy of the stitch point position using the robot arm.